(1) Field of the Invention
The invention relates to the design and operation of a lightweight portable turntable for rotating a wheelchair in tight quarters.
(2) Description of Related Art
Conventional wheelchairs or powerchairs, in particular rear wheel drive chairs, are not designed to rotate on a central axis and are difficult to maneuver in tight quarters and cannot rotate or turn on a short axis like modern mid wheel drive powerchairs which can rotate on a short axis. However, the rear wheel drive powerchairs are far more suitable for travel over rough terrain such as in fields or in wooded areas. Situations are encountered wherein the ability to rotate a wheelchair in tight quarters is required in sporting events wherein travel over rough terrain is required to reach a position where short axis rotation is desirable. Examples of such occasions include hunting and fishing trips. To overcome this problem it is desirable to provide a separate turntable for the powerchair at the short axis location.
Wheelchair turntables have been described for various applications. However, safety concerns have not been sufficiently addressed. These concerns become particularly important when the wheelchair is in motion, such as in a car or bus. Moreover, applications for modern, motororized and therefore heavy wheelchairs have also not been sufficiently addressed.
Wess, et. al., in U.S. Pat. No. 6,568,646 describes a circular turntable mounted rotatably on a base. In one embodiment, the turntable is supported by central conical roller bearings assisted by anti-friction pads between turntable and the base. In a second embodiment the turntable is supported by ring bearings formed by multiple plastic spheres disposed in two circular grooves in the base, concentric with the turntable. Wess provides a rod which effectively locks the turntable to the base of the unit, thereby preventing the table from rotating during positioning of the wheelchair or when the table is not occupied.
Lamb, U.S. Pat. No. 4,339,224 describes a circular compartment containing multiple turntables to accommodate wheelchairs in a public transportation vehicle such as a bus. A padded center-post and padded walls are provided as cushioning for the chair and its occupant in the event of a sudden jolt of the vehicle. However, no provisions are made to secure the wheelchair itself, much less the occupant.
Whitfield, U.S. Pat. No. 7,040,248 B1 shows a turntable for holding a wheelchair on a boat or truck. The chair is fastened to the turntable with U bolts and the turntable is stabilized against vehicle movements.
Constantin, U.S. Pat. Nos. 4,690,364 and 4,754,946, teaches a wheelchair supporting platform onto which the wheelchair is securely fastened with bolts. The platform is rotatably mounted onto a base by a shaft which extends through an opening in the base. In operation, the shaft is fitted with a retaining washer which permits rotation but does not permit the shaft to be pulled out of the opening. Thereby the wheelchair can be safely secured in a moving vehicle,
Lanzillotta, et. al., U.S. Pat. No. 4,759,684 teaches, a wheelchair supporting platform which raises the wheelchair in the manner of a barber chair and also permits rotation thereof. The wheelchair is rolled onto the platform but is in no way secured to the platform.
Sheets, U.S. Pat. No. 5,220,116, describes a rotatable shooting platform for a quadriplegic which has front and rear stops against the wheels of a wheelchair to prevent its forward or backward movement. This is particularly important to prevent gun recoil from driving the chair backwards and off the platform. However, these stops, which are permanently fastened to the platform, make it difficult to subsequently move the wheelchair off the platform. In a second embodiment, a reversible electric motor, operated by the hand of the occupant, rotates the turntable.